This invention relates generally to a safety shut-off valve which cuts off flow automatically in response to a leak or break in a flow line. More particularly, the present invention relates to a safety shut-off valve particularly useful in hydraulic lines wherein a rupture of any of the liquid-containing lines is apt to disable the entire hydraulic system and may result in serious consequences. The present invention responds to an abnormal flow condition downstream in a hydraulic line and advantageously, seals off flow so that a ruptured part does not disable the entire system.
A ruptured hydraulic line has previously proven fatal by triggering various past airplane crashes attributable to hydraulic pressure loss. For this reason, a safety shut-off valve for use in hydraulic lines is especially important. As will be known by those skilled in the art, there exist a number of devices which are designed to control flow, and to act as a shutoff in the event of a leak. These devices generally fall into two major categories, namely the shock operated type and the flow or pressure operated type. The shock operated device is designed to operate to shut off flow in the event of a major shock, such as that of an earthquake or the like. Examples of such devices are found in U.S. Pat. No. 3,747,616, to Lloyd, in U.S. Pat. No. 3,768,497, to Mueller, in U.S. Pat. No. 4,091,831, to Pazmany, in U.S. Pat. No. 4,336,818, to Dauvergne, and in U.S. Pat. No. 4,485,832, to Plemmons et al. These devices are all designed for use with gas lines, and do not address the problem of breaks or leaks in the line downstream of the devices.
The second approach, which causes a shutoff of flow in the event of an overly large flow rate or an excess pressure drop across the device is illustrated, for example, by U.S. Pat. No. 2,659,383 to Frager, U.S. Pat. No. 4,522,229 to Van de Moortele, U.S. Pat. No. 4,665,932, to Quenin. All three of these devices are designed primarily for industrial applications, and are large, complex, and expensive, and therefore, are less than ideal. Prior art that is exemplary of the second approach generally requires undesirable complex utilization of a multitude of moving parts. Moreover, many prior flow control devices are not designed to be responsive to the situation contemplated by the present invention, namely a leak in downstream plumbing.
The second approach, i.e. causing a shutoff of flow in the event of an overly large flow rate, was the basis for Applicant's previously patented fluid shutoff device, Pat. No. 4,880,030, issued Nov. 14, 1989 and titled "Safety Flow Control Fluid Shutoff Device."
The main causes of leakage are ruptured pipes, tubes or fittings; supply lines and other flow promoting equipment; rusty or aging components, poor installation practices, poor quality materials, and pressure surges. With so many different factors that can create in-line failures and runaway leaks, one can readily realize the need for a fluid shutoff safety device. This need is accentuated considering the massive difficulties that ensue in the wake of a failure involving a hydraulic line which provides hydraulic power in aircraft.
The vast array of prior flow control devices prohibits a detailed listing of the many problems associated with the various types of previous flow shut-off inventions. Noteworthy are those prior problems which the present invention is directed towards addressing. One such prior art drawback is evident in the general type of shut-off valves that characteristically execute flow stoppage in response to a pressure change in the flow line, rather than providing for flow shut-off at a predetermined, preselected pressure. There is, therefore, a significant need, especially for application in hydraulic systems, for an improved shut-off valve that can be relied upon to execute flow stoppage at a predetermined pressure that can be pre-selected during manufacturing of the improved flow control device.
Another drawback associated with some prior flow control devices is that said prior devices disadvantageously have structural or operational characteristics that induce turbulence in the flow stream. Usually, such turbulence undesirably results in pressure loss in the flow system. Exemplary of those elements which promote turbulence in prior flow control devices are the inclusion of complex shaped working components that are less than ideally streamlined, the use of sharp edges on structural features that contact the flow stream, and the practice of inducing sharp changes in the direction of the flow stream. There is needed, therefore, an improved shut-off valve that operates so as to minimize the creation of turbulence in the flow stream, especially while the shut-off valve is operating in an open mode to allow flow to be normally conducted.
Yet another prior art problem is apparent in those previous flow control devices which are generally characterized as ball and check valves. Disadvantageously, many prior shut-off valves are operable only between the extremes of being either completely open (to allow full flow) or completely closed (to prohibit any flow), whereas it would be advantageous to provide an improved shut-off device that could provide a gradual change in flow conditions from zero flow to full flow. The advantage of providing a flow control device operable to allow for gradual change in the flow intensity is that one wishes to avoid shockwaves in the flow system. That is, a prior shutoff valve that abruptly slams shut to execute flow stoppage undesirably unleashes a shock to the flow system which can only have a negative overall impact. In general, it is preferable to avoid an operating action that involves switching abruptly from one extreme (full flow) to the opposite extreme (zero flow) in order to prevent destructive shock to the flow system apparatus. Moreover, an improved flow control device should also address the reverse situation in that the shut-off valve should, preferably, be capable of allowing the flow to be gradually restored from zero flow to full flow following repairs to a damaged flow line. An important factor that is a determinant in whether gradual flow change or abrupt flow change will be achieved is the manner in which a shut-off valve employs its closure member to effect flow stoppage and flow resumption, specifically the seating (or closure) action of the closure member.
In addition to the need for an improved flow control device which addresses the afore-mentioned concerns, it is desirable that such an improved shut-off valve advantageously should stay closed to prevent flow until any downstream problem in the flow line is finally fixed. The needed shut-off device desirably should have an extended highly reliable operating life, and must operate flawlessly and immediately upon the occurrence of a break or leak in the flow line to shut off the flow before extensive damage occurs. In hydraulic system applications, the needed flow control invention must automatically and immediately execute flow shutoff in order to ensure that hydraulic fluid does not leak out in such a sufficient quantity so as to cause a dramatic loss in hydraulic pressure, and an accompanying dreaded disabling of the hydraulic system (which could prove fatal in aircraft applications). The present invention fulfills these needs and provides further related advantages.